In prior art front ends for a broadband optical receiver preamplifiers are typically used together with, e.g., PIN or avalanche photodiodes to convert high-frequency optical signals transmitted over optical waveguides into electric signals suitable for demodulation.
An outline of commonly used front ends equipped with PIN photodiodes or avalanche photodiodes (APD) is contained, for example, in "EPO Applied Technology Series Vol. 5", entitled "Optical Fibres",Chapter III, pp. 446 et seq.
With such front ends, substantially linear and high gain, which requires a good signal-to-noise ratio, is to be achieved over as wide a frequency range as possible.
The best results have so far been achieved with avalanche photodiodes in conjunction with preamplifiers using a gallium arsenide field-effect transistor (GaAsFET) as the front end and designed as transimpedance amplifiers. However, avalanche photodiodes are still very expensive compared with PIN diodes, and field-effect transistors, particularly low-capacitance GaAs field-effect transistors, generate high so-called 1/f noise in the low frequency range. This noise affects, for example, the transmission of additional low-frequency signals or the transmission of analog signals.
As indicated in "Electrical Communication", Vol. 56, No. 4, 1981, page 356, section entitled "Schlu.beta.betrachtungen", progress toward improving optical receiver performance was expected mainly of the development of improved avalanche photodiodes and the integration of detector and subsequent field-effect transistor (PIN-FET approach).
The first-mentioned reference also shows preamplifiers using bipolar transistors and avalanche photodiodes which are claimed to have reached data rates of 500 Mb/s (p. 455, FIG. 3.32) and 1.12 Gb/s (p. 460, FIG. 3.4). The reference gives no details of the implementation and cost of the circuits shown.